In conventional methods, a coarse adjustment of the angle takes place with the aid of the mentioned precontrol while the fine adjustment takes place via an engine-speed closed-loop control. One such conventional method will be explained in greater detail with reference to FIG. 2.
The throttle flap (DK) 10 has an opening angle which is to be adjusted and is arranged on an internal combustion engine 11. An actuator element (not shown) is assigned to the throttle flap 10 and is driven by the output signal of an idle controller 12 in order to adjust the throttle flap angle to a desired value DK.sub.-- SOLL. For this purpose, a first subtraction point 13 receives the above-mentioned desired value DK.sub.-- SOLL as well as the actual value DK.sub.-- IST in order to form the difference between the two values. The position controller 12 controls based on this difference, that is, based on the control deviation in the opening angle.
The desired value DK.sub.-- SOLL for the throttle flap angle is made up of two components, namely, a precontrol value DK.sub.-- VOR and a control value DK.sub.-- REG which are combined additively in a precontrol point 14. The value DK.sub.-- REG is the output signal of an engine-speed controller 15 which forms this output signal in dependence upon the control deviation between an engine-speed desired value N.sub.-- SOLL and the engine-speed actual value N.sub.-- IST with the control deviation being generated in a second subtraction point 16. The desired engine speed N.sub.-- SOLL is read out from an engine-speed characteristic field 17 in dependence upon the engine temperature. The precontrol value DK.sub.-- VOR is the second value supplied to the precontrol point 14 and is the result of a multiple modification of a basic desired value DK.sub.-- SOLL for the opening angle of the throttle flap. Base desired values are read out from an opening-angle characteristic field 18 in dependence upon the engine temperature. A modification then possibly takes place in a multiplier point 19 which will be discussed further below. Thereafter, a multiplicative or additive combining with correction variables takes place in a combining point 20. The correction variables are supplied from a correction component 21. Load-dependent corrections are of concern here. For example, to maintain the desired idle engine speed, the throttle flap angle must be increased if an air conditioner is switched on.
The correction in the multiplier point 19 is essential in connection with the following. A start phase correction is of concern here having a time-reduced multiplier factor FAKSTA represented by block 8 and which is set to a maximum value such as the value two when the engine is started and then decays to the value one within several seconds. The start of the engine is indicated via the signal of an ignition lock 22. As a result of the foregoing, the temperature-dependent base desired value DK.sub.-- GRUNDSOLL for the opening angle of the throttle flap is modified to increase this angle during the starting phase to ensure that the engine 11 is supplied with more air and more fuel in this time duration.
It is noted that for an actual idle control still further correction values are effective and that an adaption is especially present. Details of this kind are, however, without significance with respect to the subject matter at hand.
The known method described above with respect to FIG. 2 has the disadvantage that the start factor FAKSTA is always operative in the start phase. This leads to the condition that even during starting of an engine which is warm, a throttle value DK.sub.-- SOLL occurs which is relatively high and which causes an unwanted increase in engine speed for this operating condition. This disadvantage has up until now been accepted in order to maintain, when starting a cold engine, the increase of the opening angle of the throttle flap which is required during starting.
The problem has long existed to provide a method and an arrangement for precontrolling the opening angle of a throttle flap to permit, for a simple operation, an increase of the opening angle of the throttle flap in the starting phase of a cold engine which, however, does not lead to this kind of increase for a warm engine.